1. Field of the Invention
The present invention relates to a motion image processing apparatus and method and, more particularly, to an image processing apparatus and method which can reduce transmission, storage, and display data amounts by detecting an image change and can be suitably used for an image transmission apparatus, an image storage device, and a motion image display device. That is, the present invention can be used for a monitoring apparatus for transmitting and storing images in a monitoring area, a video conference apparatus, a general-purpose computer or video server which handles motion images, and the like.
2. Related Background Art
In the field of monitoring, e.g., road monitoring and night monitoring, apparatuses which reduce the cost for monitoring by transmitting and monitoring images obtained by photographing a monitoring area with a TV camera or storing the images in a storage device have been used. In this case, the transmission and storage data amounts are reduced by detecting an image change and outputting image data only when an image change occurs.
In recent years, image data are exchanged and stored between remote places via a communication network such as a WAN (Wide Area Network) or a LAN (Local Area Network) in many instances, like a video conference, without the intention of monitoring. In addition, with an improvement in the performance of a general-purpose computer, the computer can transmit and store motion images as well as displaying motion images.
Since image data amounts too much, a dedicated device is required to perform detection processing an image change at a speed as high as that of image processing. If there is no such a dedicated device, an image temporarily stored is processed for a long period of time.
Recently, however, image data is transmitted, stored, or displayed by using a general-purpose computer in many instances. For example, video conference systems using general-purpose computers have become popular, as described above. Demands have therefore arisen for a method of performing detection processing of an image change at a speed as high as that of image processing without using any dedicated device.
Various methods associated with the above image change detection method have been proposed. A relatively easy method is a method of detecting a change area by obtaining a difference between two images. According to this easy method, even a general-purpose computer can execute detection processing at a sufficient processing speed.
As methods of detecting a change area on the basis of a difference between two images, typical methods are a method of detecting a change area on the basis of a difference between a background image photographed in advance and a currently photographed image, and a method of detecting a change area on the basis of a difference between two frames adjacent to each other along the time base.
There has been proposed an apparatus based on the latter method of detecting a change area on the basis of a difference between frames to record images in a monitoring area on a VTR, wherein an image change is detected and an image is recorded on the VTR only when the image change occurs.
Many limitations are, however, imposed on the use of the method of detecting a change area on the basis of a difference between a background image and a current image. For example, a background image having no moving object must be prepared.
According to the method of detecting a change area on the basis of a difference between frames adjacent to each other along the time base, when an image change is moderate, the difference is small. In this case, therefore, it is difficult to detect a change area.
Furthermore, in the method of detecting a change area on the basis of a difference between images, erroneous detection of a change area tends to occur because of flickering of the light source or mixing of noise in a photoelectric scanning unit or an electronic circuit unit, and the like.
The present invention has been made in consideration of the above situation, and has as its object to easily and reliably detect an image change at a sufficiently high processing speed without using any dedicated device.
In order to achieve the above object, according to an aspect of the present invention, there is provided an image processing apparatus (method) including input means (step) for inputting a continuous image signal, detection means (step) for detecting a frame change in an image by comparing the image signal input by the input means (step) with a reference image signal, and storage means (step) for updating/storing the image signal input by the input means (step) as the reference image signal in units of frames in accordance with an output from the detection means (step).
It is another object of the present invention to accurately detect an image change without being affected by change areas (erroneously detected small areas dispersing randomly, in particular) erroneously detected because of flickering of a light source or mixing of noise in a photoelectric scanning unit, an electronic circuit unit, or the like.
In order to achieve the above object, according to another aspect of the present invention, there is provided an image processing apparatus (method) including input means (step) for inputting a continuous image signal, change component extraction means (step) for extracting change components between images by comparing the image signal input by the input means (step) with a reference image signal, erroneous extraction correction means (step) for detecting and removing an erroneously extracted change component from the change components extracted by the change component extraction means (step), and image change discrimination means (step) for discriminating an image change in the image signal on the basis of the change component corrected by the erroneous extraction correction means (step).
Other objects, features and advantages of the invention will become apparent form the following detailed description taken in conjunction with the accompanying drawings.